The present invention relates in general to power tools. In particular, the present invention relates to a depth adjusting system for a power tool such as a power-driven screwdriver.
Power-driven screwdrivers frequently are equipped with depth locators that are releasably mounted to the nose of the tool and surround the screwdriver bit for adjustably setting the depth to which the head of a screw will be set into a workpiece. In particular, the axial position of the depth locator is typically adjustable relative to the tool bit so as to control the extent to which the screwdriver bit protrudes from the end of the depth locator. Consequently, as the screw is driven into the workpiece, the end of the depth locator will contact the surface of the workpiece thereby unloading the axial pressure on the screwdriver bit required to maintain engagement of a clutch mechanism in the power-driven screwdriver.
It is desirable for depth adjusting systems to be easily adjusted and also readily removable from the tool housing while maintaining the depth setting to enable the operator to conveniently replace the screwdriver bit. Known depth adjusting systems are shown in U.S. Pat. Nos. 4,647,260 to O'Hara et al., and 5,380,132 to Parks. These patents are both assigned to the assignee of record of the present invention and are expressly incorporated herein by reference.
The depth adjusting system disclosed in U.S. Pat. No. 4,647,260 comprises a two-piece molded plastic subassembly that is connected to the forward end of the housing of the power tool. The subassembly comprises an adjustment collar that is mounted to the nose portion coaxial with the tool bit so as to be restrained from axial movement but free to rotate relative to the housing, and a depth locator that is threadably connected to the adjustment collar and restrained from rotating relative to the housing but free to move axially relative to the housing in response to rotation of the adjustment collar. The adjustment collar is provided with an internal annular flange that is engageable through a snap-action with a retaining ring located on the nose portion of the housing. In addition, indexing means in the form of a plurality of circumferential resilient fingers are provided on the adjustment member for engaging detents on the nose portion of the tool and serve to settably maintain the adjustment member in a predetermined angular position relative to the housing. The resulting depth adjusting system disclosed in this patent enables an operator to disconnect the subassembly by unsnapping the adjustment member from the housing without disturbing the previously set depth adjustment.
U.S. Pat. No. 5,380,132 discloses a depth adjusting system for a power tool that comprises an adjustment collar releasably fitted to the housing of the tool and a depth locator which screws onto the collar. The adjustment collar has a forward cylindrical portion and an enlarged rearward cylindrical portion that includes a pair of diametrically opposed, axially extending cantilever spring fingers for detachably connecting the adjustment collar to a circular opening in the housing. The free ends of the spring fingers are provided with a hook and groove that are adapted to engage and mate with a corresponding circumferential groove and rib in the housing opening, thereby permitting relative rotation of the adjustment collar to the housing which serves to set the relative axial position of the depth locator. The adjustment collar and depth locator subassembly may be removed from the housing without disturbing the depth setting by depressing the spring fingers sufficiently to release the hooks from the groove in the housing.
While prior known devices such as those discussed above have proven to be commercially successful, it is further desirable, however, to provide a depth adjusting system that is convenient to remove from the nose portion of the housing and that provides components that are less subject to wear, thereby resulting in a system having reliability over a longer period of time.
The present invention comprises an improvement over prior known depth adjusting systems, including those disclosed in the aforementioned patents. More particularly, the present invention provides an improved interface between the depth adjusting subassembly and the forward end of the nose portion in the form of a pair of arcuate spring members. In the preferred embodiment, each of the arcuate spring members is constructed of hardened steel to reduce physical wear of the interface between the depth adjusting subassembly and the nose portion. In normal operation, the engagement of one or more arcuate ribs integrally formed into each of the arcuate spring members with an internal groove formed in an adjustment collar enables the adjustment collar to be freely rotated relative to the nose portion. Preferably, the arcuate spring members further include detent projections to positively maintain the adjustment member in a set angular position relative to the tool housing.
In one form, the depth adjusting system of the present invention is adapted for use with a power tool having a housing. The depth adjusting system includes a nose portion connected to the housing and a subassembly including an adjustment member connected to the nose portion for rotatably non-axially movement relative to the nose portion during depth adjusting movement of the adjustment member. The depth adjustment system additionally includes a depth locator member interconnected with the nose portion for axially slidable, non-rotatable movement relative to the nose portion during depth adjusting movement of the adjusting member. Further, the depth adjusting system includes a joining member for establishing releasable interconnection between the subassembly and the nose portion. The joining member includes a substantially rigid portion engaging the subassembly and a resilient portion for biasing the substantially rigid portion into engagement with the subassembly.
In a preferred form, the depth adjusting system of the present invention includes a nose portion connected to the housing and a depth adjusting subassembly for establishing a predetermined depth for setting a threaded fastener into a workpiece. The depth adjusting subassembly is releasably connected to the nose portion and includes an adjustment collar rotatably coupled to the nose portion for non-axial movement relative to the nose portion during depth adjusting movement, and a depth locator. The adjustment collar includes an inner circumferential surface defining a circumferential groove. The depth locator is threadably connected to the adjustment collar and constrained from rotating relative to the nose portion so that rotation of the adjustment collar causes axial displacement of the depth locator. The system further includes a pair of substantially identical arcuate spring members attached to the nose portion. Each of the arcuate spring members include at least one arcuate rib portion adapted to engage the circumferential groove of the adjustment collar. The arcuate spring members are additionally formed to include a plurality of cantilevered spring fingers for providing an outward bias. Further preferably, the inner circumferential wall includes a plurality of axially extending channels and the arcuate spring members include a detent projection. The detent projections and the axially extending channels cooperate to positively locate the adjustment member axially with respect to the nose portion.